This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-297699, filed Sep. 28, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an angle detector used for a structure having a rotating body rotated about a shaft, such as a gimbal mechanism, and detecting a rotation angle of the rotating body.
2. Description of the Related Art
An angle detector is used to detect the angle of rotation of a rotating body about a rotating shaft. A rotary encoder is a typical example of this kind of device.
The rotary encoder has a circular disk mounted with its center aligned with the rotating shaft and a light source and light receiving element arranged in a mutually opposite relation with the disk sandwiched therebetween. The disk has slits radiating from its center. Light reaching the light receiving element from the light source is such that, with the rotation of the rotating body, it either passes through the slits or is blocked by the disk. By counting the number of times the light passes through the slits and the number of times the light is blocked by the disk, the rotation angle of the rotating body about the rotation shaft is detected.
By the way, the performance of this kind of device, such as the resolution and accuracy, generally depends upon its size. In the rotary encoder, for example, the greater the size of the disk, the finer the slits, and hence the resolution is enhanced. In a modern precision machine, however, the installation space of the angle detector often has to be made narrower due to the dimensional restriction and the dimension of the angle detector has to be made smaller and it is difficult to obtain a required performance.
In one application of the angle detector, there are cases where, in a two-axis gimbal mechanism, the rotation angles about its axes have to be detected. The gimbal mechanism is mounted, for example, at a nose of a missile and used to support an optical sensor aimed at a target. Inside the missile, it is very difficult to secure its installation space. For the angle detector in such an application it becomes more and more difficult to secure a required performance.
Such a conventional angle detector depends for its performance upon its own dimension. In the case where the installation space is restricted, there is an inconvenience that required performance cannot be achieved.
It is accordingly the object of the present invention to provide an angle detector which can alleviate its dimensional restriction and, by doing so, achieve improved performance.
The present invention is directed to an angle detector for detecting an angle of rotation of a rotating body about a rotation shaft. The angle detector according to the present invention includes a sensor head mounted on the rotating body and having induction coils to which an AC signal is applied and a rod arranged opposite to a moving focus of the sensor head moved with the rotation of the rotating body and having a plurality of magnetically responding members arranged and fixed, wherein the rotation angle of the rotating body is detected from output signals induced in the induction coils by moving the sensor head relative to the rod.
The amount of relative movement between the sensor head and the rod is found by detecting, for example, a phase variation of the induced output signals. The sensor head and rod have the same curvature radius and the movement amount is converted to the rotation angle of the rotating body through the division of the movement amount by the curvature radius.
In the above-mentioned structure, the rotation angle of the rotating body corresponds to the amount of movement of the sensor head along the rod (or the amount of movement of the rod along the sensor head) The amount of movement of the sensor head along the rod is detected by output signals induced in the induction coils.
The sensor head or rod can be provided in such a state as to be buried, for example, into the rotating body itself and support mechanism, etc., supporting the rotating body. Therefore, it is possible to increase the size of the angle detector itself. That is, it is possible to alleviate the dimensional restriction of the angle detector and hence to promote improved performance of the angle detector.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.